Optical Semiconductor device

Abstract

An optical semiconductor device has a semiconductor substrate, a semiconductor region and heater. The semiconductor region has a stripe shape demarcated with a top face and a side face thereof. The stripe shape has a width smaller than a width of the semiconductor substrate. An optical waveguide layer is located in the semiconductor region. A distance from a lower end of the side face of the semiconductor region to the optical waveguide layer is more than half of the width of the semiconductor region. The heater is provided above the optical waveguide layer.

1 . An optical semiconductor device comprising:
 a semiconductor substrate;   a semiconductor region that has a stripe shape demarcated with a top face and a side face thereof,   the stripe shape having a width smaller than a width of the semiconductor substrate,   an optical waveguide layer being located in the semiconductor region,   a distance from a lower end of the side face of the semiconductor region to the optical waveguide layer being more than half of the width of the semiconductor region; and   a heater provided above the optical waveguide layer.   
     
     
         2 . The optical semiconductor device as claimed in  claim 1 , wherein the width of the semiconductor region is a width at a region of the semiconductor region where the optical waveguide layer is positioned. 
     
     
         3 . The optical semiconductor device as claimed in  claim 1 , wherein:
 the semiconductor region has an upper cladding layer and a lower cladding layer,   the optical waveguide layer being between the upper cladding layer and the lower cladding layer; and   the upper cladding layer, the lower cladding layer and the semiconductor substrate are composed of InP.   
     
     
         4 . The optical semiconductor device as claimed in  claim 1 , wherein an air region is adjacent to a side face of the semiconductor region. 
     
     
         5 . The optical semiconductor device as claimed in  claim 1 , wherein the side face of the semiconductor region is covered with an insulator having a thermal conductivity lower than that of the semiconductor region. 
     
     
         6 . The optical semiconductor device as claimed in  claim 5 , wherein the insulator is composed of polyimide. 
     
     
         7 . The optical semiconductor device as claimed in  claim 1 , further comprising a gain region providing a gain to a light propagating in the optical waveguide layer. 
     
     
         8 . The optical semiconductor device as claimed in  claim 7 , wherein the gain region has a width larger than that of the semiconductor region. 
     
     
         9 . The optical semiconductor device as claimed in  claim 7 , further comprising a temperature control device where the gain region and the semiconductor region are mounted. 
     
     
         10 . The optical semiconductor device as claimed in  claim 9 , further comprising a temperature control device mounting partly the substrate of the gain region side. 
     
     
         11 . The optical semiconductor device as claimed in  claim 1 , wherein the lower end of the side face of the semiconductor region is positioned at a position lower than a surface of the semiconductor substrate.